the pressure cooker part of these bombs. joe, what are you learning? >> wolf,alawenforcementofficial told me today that authorities are preparing for a long and slow investigation here and it starts with pieces of the explosive devices scattered along an enormous crime scene. even before the dust started to settle, authorities were asking what kind of explosive device created this. the picture of the bombs now starting to emerge is that they were deadly but crude. a federal law enforcement official with knowledge of the boston bomb investigation tells cnn the bombs were hidden in bags inside a metal pressure cooker. a law enforcement source also told cnn that it's likely but not certain that a timing device was used to detonate the bomb. emergency room doctors said they believed the bombs contained bbs and nails intended by the bomber to kill or maim as many people as possible. >> there were a variety of sharp objects that we found in their bodies, probably this bomb had multiple metallic fragments in them and we removed them. >> mike bouchard is a former top official with the bureau of a

that from congressionalandlawenforcementsources, myself and mike brooks, who actually got the first tip on this story. now, we don't know which senate office this was original hi sent to. but we do understand that this envelope was tested positive. and a first routine test, it was retested two more times, so it was tested three times all together. each time it came up positive. and that's according to a law enforcement source who said that afterward, it was sent to maryland on an offsite facility to do further testing. we should remind our viewers, after the anthrax scare back in 2001, in the fall of 2001, when a couple of senate offices received envelopes with anthrax in it, they changed the way that the mail is distributed on capitol hill, so they now begin for the most part in an offsite. so this was intercepted at an offsite mail facility, was not done -- did not make its way to the capitol. so this is the information that we have so far. i can also tell you that ted barrett, cnn's congressional producer, asked senate majority leader harry reid about this, what we were learning, and

,lawenforcementofficials are keeping a very close eye on the internet, specifically sites that show people how to make destructive devices. nbc's senior investigative correspondent lisa myers has that part of the story, good morning. >> matt, good morning to you. regardless of who committed this atrocity it's clear these days that anyone with a grievance and the will can learn how to become a terrorist simply by going online. now authorities are trying to use some of these sites to their advantage. the latest evidence bomb makers have taken their teachings to the web this online al qaeda publication posted last month, a guide to carrying out terror attacks including detailed illustrated recipes for pressure cooker bombs, the kind investigators say was used in boston. >> the internet has brought terrorism to the web. it's made it go viral. anybody can look online and find out how to make a bomb. it is a frightening development. >> a similar terrorist manual, how to make a bomb in the kitchen of your mom, was posted three years ago. prosecutors say it was used by this former muslim-am

to find the person still there? >> well, absolutely. and that's why you've heardfederallawenforcementofficials say they're looking at planes coming in and out of boston, even as we speak. as the investigation is ongoing. and one of the things we ought to mention is on all of these component parts, investigators will be looking for latent fingerprints. they'll be looking for dna samples. because somebody had to touch it to put it together. so it's likely that they will have left some mark on this that will be distinctive to them. so all of this will come together to try and help them to quickly identify. what juliette says about it being a boston case is absolutely right. we looked at prior terrorism cases, both successful and unsuccessful cases that have been disrupted, and each time you trace back sort of the perimeter you find that devices are put together in close proximity to where the attack is actually launched. so that's -- investigators understand that and will begin to work from the crime scene outward. >> all right, fran townsend, juliette chi up, our thanks to you. >> let'

of the things we have been talking about in the last day and a half in this investigation ishowlawenfo e enforcement officials will be looking for a bomb-making signature. some sign that shows where the bomb was put together and where they received their instructions. as you're looking at these pictures, are these the types of things that give you a sense of these signatures? >> quite reminiscent of some major cases i worked on while with ncis. using a device like this, almost always there are components left behind. the crime scene processing and technicians making the initial assessment and even chemical tests are being matched up at the national center, tdac at quantico, virginia. it will be confirmed whether the device flagrated or detonated which would indicate a higher explosive. all of these things produce leads for investigators to run down. >> john and i were talking during the commercial break going back to the olympic park bombings in 1996, the process investigators went through finding the nails that shot out of the bomb, tracing the nails back to the manufacturer and finding

tonight thatfederallawenforcementsource confirms that prosecutors are preparing search warrants. most likely to be executed tomorrow. a limited number in the boston area in their continuous search for evidence in this case. that suggests that there are at least some leads, but mr. deloria made clear the investigation is in its infancy, and the number of -- the search for suspects and motives remains wide open. >> leiter, what does this mean? i mean, is there anything here that's a breakthrough? the public clearly wants to see what happened and why, but at the same time, you don't want to rush and -- and bring in something or someone that you can't really get the evidence to back up. so is there any breakthrough at all in any of this? >> well, it's still relatively early, but i think there are two things that are really important. the type of bomb doesn't tell us all that much. lots of different groups have used this bomb. you can find out how to make a pressure cooker bomb on the internet. >> wait a minute. you can find out how to make this bomb on the internet. so we don't -- we can'

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